1. Field of the Invention
The present invention relates to an illumination device equipped with an optical filter that converts luminance and/or color tone of a light beam irradiated by a light source, as well as a projector.
2. Description of Related Art
Conventionally, projectors have often been used for presentations at conferences, scientific meetings, exhibitions and the like. Such a projector is used as a data projector for mainly displaying characters, graphs and so on. Further, the projectors have remarkably been promoted recently, and such a projector having been used for the purpose of watching movies etc. at home as a home-theater projector.
In order to display characters and so on, the data projector requires displaying high-luminance image. On the other hand, in order to display video pictures of TV programs and movies etc., the home-theater projector requires to display high-chroma image (high-saturation image), which is colorful image emphasized on color reproducibility. Therefore, in terms of the image quality of the display image, there are various requirements such as luminance, chroma saturation, contrast or the like depending on the purpose of the projector. To meet with the requirements, there has been known a projector in which a filter is provided on an optical path in an optical system that modulates a light beam irradiated by a light source in accordance with image information to form an optical image, so that luminance, chroma saturation or the like is adjusted by the filter (for example, see patent document 1; JP2001-174774A, page 5, FIG. 3).
The filter applied to such projector has a filtering element formed corresponding to the pitch of a lens element of an integrator lens. The filter is moved so that the filtering element is inserted at the focal position of the light beam irradiated from the integrator lens.
However, while it is disclosed in the patent document 1 how the filter section is formed corresponding to the focal position of the light beam irradiated by the integrator lens and how the filter moves, the direction and the amount of the movement of the filter are not indicated.
Besides, not only the specific configuration of the filter and that of the mechanism for moving the filter are not disclosed, but also the method for switching between the high-luminance image and high-saturation image is not specifically described.